40 
PSYCHE 
[April-June 
head, thorax and .chaster ; nearly always completely absent on the lower sur- 
face of the head and petiolar Ijorder. I'emora naked : tibiae with a row of 
tapering hairs on their flexor surfaces. Pubescence white, extremely short 
and sparse, so that it is almost invisible except on the upper surface of the 
gaster. 
Reddish yellow ; borders of mandibles black ; anterior border of clypeus, 
vertex, upper surface of pro-and mesonotum. femora, tibiae, apical antennal 
joints, and gaster more or less infuscated ; anal region yellow. In many speci- 
mens the upper surface of the head is more reddish than the remainder of the 
body but there is little difference in coloration between the smallest and 
largest workers. 
Described from many workers taken by Mr. A. P. l\Iorse from a flourish- 
ing colony at South Natick. INIass. This form is very closely related to some 
of the smaller American Formicac of the ritfa group. Its exact status and 
affinities, however, cannot he determined without a knowledge of the female. 
It can hardly I)e a mere variety or subspecies of F. nifa pro]ier, and it certainly 
has a very different habitus in coloration and pubescence from any of the allied 
species known to me. 
4. Formica impc.ra Wheeler. 
Of this interesting species, originally described from workers only, taken 
in the Porcupine ^Mountains of Northern Michigan, Mr,. P. Morse has 
recently discovered a colony at* Sherborne, near East Holliston, ^Massachusetts. 
It was nesting in the upright trunk of a white pine, between bark and wood, 
about three feet from the ground and contained a few of the hitherto unknown 
females. These very closely resemble in their diminutive size (4.5 mm. in 
length) and coloration the females of the species which I have descril^ed as 
F. luicrogyna, ncradcusis and ucpticiila, but the whole body, antennal scapes 
and legs are covered with long, suberect, obtuse hairs. They agree with the 
female of microgyua and differ from those of ncpticula and ncradciisis in hav- 
ing the gaster opaque and densely grayish pubescent. 
The discovery of these diminutive females not only proves that I was not 
mistaken in regarding impc.va as specifically distinct from F. nifa, but also 
indicates that, like F . difficilis and )nicrogy]ia, it is a temporary parasite in 
depauperate colonies of some other species of Formica. As a matter of fact, 
the vial containing the impc.va workers and females also contained a number 
of workers of P'. fii.<;ca var. sabacncsccus, which Air. Morse collected at the 
